Chop onion and green pepper. Wash, drain and, trim the beans and cut them diagonally into 2-inch pieces. Take beef cubes and vegetable oil in a large pot over medium heat. Cook it until the beef absorb all of its juice, stirring occasionally . Add chopped onion, chopped pepper into the pot. Saute them on a medium heat for 10 minutes then add tomato paste and continue to cook for 5 minutes. Take green beans into the pot. Add black pepper and salt. Stir them all together.Simmer it until green beans are soft. Peel the tomatoes and cut them into cubes. Place tomatoes on top of other beans. Put the lid on and cook for 20 minutes.